Evaporative recirculation cooling water system, method of operating an evaporative recirculation cooling water system and a method of operating a water deionizing system

ABSTRACT

An evaporative recirculation cooling water system, the system having a recirculation loop to recirculate water through the system, a construction with a space to cool the water in the recirculation loop by evaporation, and a water entry point to allow water into the recirculation loop. The system has a charge barrier flow through capacitor constructed and arranged to remove ions from the water and a dosing system whereby a scale inhibitor is continuously dosed into the inlet flow into the flow through capacitor.

FIELD

This disclosure relates to an evaporative recirculation cooling watersystem and to an evaporative recirculation cooling system comprising anion removal apparatus.

BACKGROUND

In recent years one has become increasingly aware of the impact of humanactivities on the environment and the negative consequences this mayhave. Ways to reduce, reuse and recycle resources are becoming moreimportant. In particular, clean water is becoming a scarce commodity.

An evaporative recirculation cooling water system may receive water froma water make-up stream. The water may be used in a recirculation loopand it may receive a heat load from, for example, a heat exchanger. Thewater may be cooled in an open space e.g. a cooling tower where thewater comes in contact with air. The cooling may be enhanced by apartial evaporation of the water in the recirculation loop and this maycause the water to be lost in the recirculation system which requires anintake of water from the make-up stream. The evaporation and theaddition of water from the make-up stream may cause an accumulation ofdissolved species in the water of the recirculation loop. Thisaccumulation of dissolved species may result in scaling in therecirculation system.

SUMMARY

U.S. Pat. No. 4,532,045 discloses a chemical ion removal apparatus forremoving ions from the make-up water to minimize the accumulation ofdissolved species. For this purpose the apparatus is provided with anion exchange system which includes weak acid cation exchange resin. Adisadvantage of the use of the weak acid cation exchange resin may bethe need for regeneration or replacement of the cation exchange resin.

Japanese patent application publication no. JP2002-310595 discloses acooling tower with a reverse osmosis membrane module which can separatecooling water into processed water from which ions are removed andconcentrated water with ions. A disadvantage of the use of a membranemay be that it also removes silica ions which are a good corrosioninhibitor and another disadvantage may be that the membrane is sensitiveto silica fouling and therefore anti-foulants may be required.

PCT patent application publication no. WO 2011-144704 discloses acooling tower with a flow through capacitor which removes hardness ionsfrom the water while leaving silica ions in the water. The hardness ionsare fed to a waste water stream. The flow through capacitor may notfunction optimally because of a scaling tendency of the waste waterstream of the flow through capacitor.

It is, for example, an objective to improve the evaporativerecirculation cooling water system.

Accordingly, in an embodiment, there is provided an evaporativerecirculation cooling water system comprising:

a recirculation loop to recirculate water through the system;

a construction with a space to cool the water in the recirculation loopby evaporation;

a water entry point to allow water into the recirculation loop;

a charge barrier flow through capacitor constructed and arranged toremove ions from the water between the water entry point and therecirculation loop; and

a scale inhibitor dosing system downstream of the water entry point andupstream of the charge barrier flow through capacitor to dose a scaleinhibitor into the water flow from the water entry point to the chargebarrier flow through capacitor.

A scaling tendency of the waste water stream of the flow throughcapacitor may be reduced by applying the scale inhibitor. By using thescale inhibitor the concentration of ions in the waste water may beincreased. The ratio of purified water with respect to waste water maythereby be improved.

The flow through capacitor may be equipped with a charge barrier that ischosen such that it allows limited to no transport of weakly dissociatedmolecules and/or charged molecules with a weight greater than 200.

The scale inhibitor may comprise weakly dissociated molecules. Themolecules may have a weight between 200 and 20,000, between 200 and10,000 or between 200 and 2,000.

The dosed scale inhibitor may comprise a charged scale inhibitor. Acharged scale inhibitor may be removed from the water by the flowthrough capacitor. However if the weight of the inhibitor is between 200and 20,000, between 200 and 10,000 or between 200 and 2,000 and thecharge barrier is constructed to substantially allow no transport ofweakly dissociated molecules and/or charged molecules with a molecularweight greater than 200, these weakly dissociated molecules and/or thecharged scale inhibitor may pass the flow through capacitor withoutbeing removed.

The flow through capacitor may comprise the water entry point and therecirculation loop so as to remove hardness ions from the water of theentry point before providing the water to the recirculation loop. Thescale inhibitor is left in the water.

The charge barrier present in the flow through capacitor may cause thedosed scale inhibitor to pass through unhindered. The same feed streamis used for the purification process as well as for the waste process,therefore the concentration of scale inhibitor in the purified streamand in the waste stream is substantially equal to the concentration ofscale inhibitor in the feed stream.

The scale inhibitor present in the waste stream will result in a lowerscaling tendency for the flow through capacitor. The scale inhibitorpresent in the purified stream will enter the recirculation loop, whereit will result in a lower scaling tendency for the recirculation loop,eliminating the need for additional scale inhibitor dosing.

The system may comprise a sensor to measure a chemical and/or physicalproperty of the water in a waste water output and/or a purified wateroutput and/or the recirculation loop, for example measure one or moreselected from: pH, alkalinity, hardness, conductance of the water, flowrate of the water and/or concentration of scale inhibitor.

The system may comprise a flow adjuster, e.g. a pump, configured toadjust the velocity of the water flowing through the flow throughcapacitor.

The system may comprise a logic circuit configured to calculate ascaling potential of waste water and/or the water in the recirculationloop in response to a function of the chemical and/or physical propertyof the water in a waste water output as measured with a sensor, as wellas the water velocity in the charge barrier flow through capacitor.

The system may comprise a controller configured to control dosing of thescale inhibitor based on the scaling potential of the waste water asdetermined by the logic circuit.

The system may comprise a controller configured to control the scalingpotential in the waste stream by adjusting the flow adjuster.

The scale inhibitor dosing system may be constructed to continuouslydose a scale inhibitor in the water from the water entry point.

In an embodiment, there is provided a method of operating an evaporativerecirculation cooling water system, the method comprising:

recirculating water through a recirculation loop of the evaporativerecirculation cooling water system;

cooling the water by evaporation;

adding water from a water entry point to the recirculation loop;

removing ions from the water from the water entry point with a chargebarrier flow through capacitor; and

dosing a scale inhibitor into the water flow from the water entry pointto the charge barrier flow through capacitor.

The charge barrier flow through capacitor may comprise a charge barriersubstantially not allowing transport of weakly dissociated moleculesand/or charged molecules with a molecular weight greater than 200.

The method may comprise dosing a scale inhibitor comprising weaklydissociated molecules.

The method may comprise dosing a scale inhibitor having a molecularweight between 200 and 20,000, between 200 and 10,000 or between 200 and2,000.

The method may comprise dosing a charged scale inhibitor.

The method may comprise continuously dosing a scale inhibitor into thewater flow.

According to an embodiment, there is provided a method of operating awater deionizing system, the method comprising:

dosing an amount of scale inhibitor into water upstream of a chargebarrier flow through capacitor; and

removing ions from the water by allowing the water with the dosed amountof scale inhibitor to flow through the charge barrier flow throughcapacitor while charging the charge barrier flow through capacitor anddirecting the water from the charge barrier flow through capacitor to anoutlet after the hardness ions have been removed.

A scaling tendency of the waste water stream of the flow throughcapacitor may be reduced by applying the scale inhibitor and thereby thedesired water savings may be reached.

The rate of addition of the scale inhibitor may be dependent on thescaling potential of the charge barrier flow through capacitor wastewater.

The rate of addition of the scale inhibitor may be dependent on thescale inhibitor concentration in the charge barrier flow throughcapacitor waste water.

The scale inhibitor concentration may be between 0.5 and 20 ppm, between0.5 and 10 ppm, or between 1 and 4 ppm.

The dosed scale inhibitor may comprise a charged scale inhibitor.

The dosed scale inhibitor may contain weakly dissociated groups, and/ormay have a molecular weight between 200 and 20,000, between 200 and10,000 or between 200 and 2.000.

The scaling potential expressed as LSI may be between 1.5 and 4, between1.7 and 3.5, or between 2 and 3.

The charge barrier flow through capacitor may be between a water entrypoint and a recirculation loop and the hardness ions may be removed fromthe water of the entry point before the water is provided to therecirculation loop, while leaving the scale inhibitor in the water.

The method may comprise measuring with a sensor a chemical and/orphysical property of the water, the chemical and/or physical propertymay be one or more selected from: pH, alkalinity, hardness, conductanceof the water, flow rate of the water and/or concentration of scaleinhibitor.

The method may comprise:

controlling charging and/or discharging of a first and second electrodeof the charge barrier flow through capacitor with a controller; and

controlling a regulator to direct water to a purified water outputduring charging of the charge barrier flow through capacitor and to awaste water output during discharging of the charge barrier flow throughcapacitor with the controller, wherein the controller controls a flowadjuster so as to adjust the water velocity in the charge barrier flowthrough capacitor in response to a function of a chemical and/orphysical property of the water in the waste water output and/or thepurified water output as measured with the sensor.

The method may comprise: calculating the scaling potential of the wastewater in response to a function of the chemical and/or physical propertyof the water in the waste water output as measured with a sensor, aswell as the water velocity in the charge barrier flow through capacitor.

The method may comprise controlling the dosing of the scale inhibitorbased on the calculated scaling potential of the waste water.

These and other aspects, features and advantages will become apparent tothose of ordinary skill in the art from reading the following detaileddescription and the appended claims. For the avoidance of doubt, anyfeature of one aspect of the present invention may be utilized in anyother aspect of the invention. It is noted that the examples given inthe description below are intended to clarify the invention and are notintended to limit the invention to those examples per se. Similarly, allpercentages are weight/weight percentages unless otherwise indicated.Numerical ranges expressed in the format “from x to y” are understood toinclude x and y. When for a specific feature multiple preferred rangesare described in the format “from x to y”, it is understood that allranges combining the different endpoints are also contemplated.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments of the invention will be described, by way of example only,with reference to the accompanying schematic drawings in which:

FIG. 1 schematically shows an evaporative recirculation cooling watersystem according to an embodiment;

FIG. 2 shows the concentration in the waste stream and in the purifiedstream as measured during a testing period of a scale inhibitorcontinuously dosed according to an embodiment of the invention; and

FIG. 3 shows the measured differential pressure normalized for the flowthrough capacitor in three periods, one period according to anembodiment.

DETAILED DESCRIPTION

FIG. 1 schematically shows an evaporative recirculation cooling watersystem ES according to an embodiment. The system comprises a water entrypoint WS to provide water to the recirculation loop RS from, forexample, tap water via a flow through capacitor FTC. The recirculationloop RS may comprise a heat exchanger HE which warms the water and aconstruction e.g. cooling tower CT provided with a space to cool thewater. An ion removal apparatus configured to remove ions e.g. a flowthrough capacitor FTC may be connected with the recirculation loop RSvia a water outlet 9 provided with a regulator e.g. valve 12 to directthe flow of water from the water outlet 9 to the recirculation circuitRS via purified water outlet 10 or to direct the flow of water to awaste water output 16.

A chemical addition system AD2 may be present to provide one or morechemical additives to the water entry point WS.

The flow through capacitor may have a housing comprising a first housingpart 1 and a second housing part 3 made of a relatively hard materiale.g. a hard plastic. By pressing the first and second housing parts oneach other, for example with a bolt and nut (not shown) the housing ismade water tight.

The housing may have a water inlet 7 and a water outlet 9. During ionremoval of the water, the water will flow from the inlet 7 to the outlet9 through the spacers 11 which separate a first charge barrier M1 and afirst electrode 13 and a second charge barrier M2 and a second electrode15 of the flow through capacitor from each other. The current collectors14 a and 14 b are clamped within the housing and connected to the powerconverter PC. By creating an electrical potential difference between thefirst and second electrode by a power converter PC, for example byapplying a positive voltage to the first electrode (the anode) 13 and anegative voltage to the second electrode (cathode) 15 the anions of thewater flowing through the spacer 11 are attracted to the first electrodeand the cations are attracted to the second electrode. In this way ions(anions and cations) may be removed from the water flowing through thespacer 11. The purified water with reduced level of hardness ions may bedischarged to the purified water outlet 10 by the valve 12.

Once the electrodes are saturated with ions the electrodes may beregenerated, whereby the ions will be released in the water in thespacer 11 in between the electrodes. The water in the spacer compartmentwith the increased ion content will be flushed away by closing thepurified water outlet 10 with valve 12 under control of the controllerCN and opening the waste water outlet 16. Once most ions are releasedfrom the electrodes and the water with increased ion content is flushedaway via the waste water outlet 16 the electrodes are regenerated andcan be used again for attracting ions.

A power converter PC under control of the controller CN is used toconvert the power from the power entry point PS to the right electricalpotential. The electrical potential differences between the anode andthe cathode are rather low, for example lower than 12 volts, lower than6 volts, lower than 2 volts or less than 1.5 volts. The electricalresistance of the electrical circuit should be low. For this purpose,current collectors 14 a which are in direct contact with the firstelectrodes are connected to each other with the first connector 17 andthe current collectors 14 b which are in direct contact with the secondelectrodes are connected to each other with the second connector 19. Thecurrent collectors 14 a and 14 b may be made substantially metal free tokeep them corrosion free in the wet interior of the housing and at thesame time cheap enough for mass production.

The charge barriers M1 and M2 comprise a membrane, selective for anionsor cations or certain specific anions or cations, and may be placedbetween the electrode and the spacer. The charge barrier may be appliedto the high surface area electrode layer as a coating layer or as alaminate layer.

Suitable membrane materials may be homogeneous or heterogeneous.Suitable membrane materials comprise anion exchange and/or cationexchange membrane materials, desirably ion exchange materials comprisingstrongly dissociating anionic groups and/or strongly dissociatingcationic groups. Examples of such membrane materials are Neosepta™ rangematerials (from Tokuyama), the range of PC-SA™ and PC-SK™ from PCA GmbH,ion exchange membrane materials from Fumatech, ion exchange membranematerials Ralex™ (from Mega) or the Excellion™ range of heterogeneousmembrane material (from Snowpure).

The charge barriers M1 and M2 are chosen such that they allow limited tono transport of weakly dissociated molecules and/or charged moleculeswith a weight greater than 200. The same feed stream is used for thepurification process as well as for the waste process, therefore theconcentration of scale inhibitor in the purified stream and in the wastestream is substantially equal to the concentration of scale inhibitor inthe feed stream.

The electrodes 13, 15 may be produced from a substantially metal freeelectrically conductive high surface area material, such as activatedcarbon, carbon black, carbon aerogel, carbon nanofibers, carbonnanotubes, graphene or a mixture thereof, which are placed on both sidesof the current collector. The high surface area layer is a layer with ahigh surface area in square meters per weight of material, for examplemore than 500 square meters per gram of material. This set-up may helpensure that the capacitor works as an electrical double layer capacitorwith sufficient ion storage capacity. The overall surface area of even athin layer of such a material is many times larger than a traditionalmaterial like aluminum or stainless steel, allowing many more chargedspecies such as ions to be stored in the electrode material. The ionremoval capacity of the ion removal apparatus is thereby increased.

A sensor SN1 configured to measure a chemical and/or physical propertyof the water in the purified water outlet 10 may be included in thesystem. The sensor SN1 measures one or more selected from: alkalinity,hardness, flow rate of the water, conductance of the water, and/orconcentration of scale inhibitor in the purified water outlet 10.

A sensor SN2 configured to measure a chemical and/or physical propertyof the water in the waste water outlet 16 may be included in the system.The sensor SN2 measures one or more selected from: alkalinity, hardness,flow rate of the water, conductance of the water, and/or concentrationof scale inhibitor in the waste water outlet 16.

A sensor SN3 configured to measure a chemical and/or physical propertyof the water in the recirculation loop RS may be included in the system.The sensor SN3 measures one or more selected from: alkalinity, hardness,flow rate of the water, conductance of the water, and/or concentrationof scale inhibitor in the recirculation loop RS.

A sensor P configured to measure a pressure differential between thewater inlet 7 and water outlet 9 of the flow through capacitor may beincluded in the system.

The ion removal apparatus may comprise a flow adjuster FA, for example,a pump, configured to adjust the velocity of the water flowing throughthe flow through capacitor FTC.

The evaporative recirculation cooling water system may comprise a firstaddition device AD1 configured to provide one or more chemical additivesto the recirculation loop RS. The first addition device AD1 may beconnected to tanks CI and BIO to provide a corrosion inhibitor and abiocide respectively to the water. As depicted the addition device AD1adds one or more chemicals to the water in the recirculation loop RS,however the one or more chemicals may also be provided in the watermake-up stream after the FTC. By locating the flow through capacitor FTCbetween the water entry point WS and the addition device AD, theaddition device AD may add the corrosion inhibitor CI and the biocideBIO after the water has passed the FTC. The one or more chemicaladditives will therefore not influence or harm the working of the FTC.

The evaporative recirculation cooling water system may comprise a secondaddition device AD2 configured to provide a chemical additive to thewater entry point WS. The second addition device AD2 may be connected totank SI to provide a scale inhibitor to the water. By providing a scaleinhibitor that is weakly dissociated and/or has a high molecular weightbefore the flow through capacitor FTC, the scale inhibitor is present inboth the water in the purified water outlet 10 and the water in thewaste water outlet 16. As the purified water outlet feeds the coolingtower recirculation loop RS, the scale inhibitor will also be present inthe water in the cooling tower recirculation loop RS. The scaleinhibitor will therefore reduce the scaling potential for both the FTCas well as for the cooling tower.

A logic circuit LC may be connected to sensor SN1 and/or SN2 and/or P soas to calculate a scaling potential of the water in the waste wateroutlet 16 and/or the recirculation loop RS in response to a function ofthe chemical and/or physical property of the water and/or the scaleinhibitor concentration in the waste water outlet 16 and/or the purifiedwater outlet 16, as well as calculate the water velocity in the FTCand/or the pressure drop over the FTC. The sensor inputs may also beobtained from preset values.

A logic circuit LC may be connected to sensor SN3 so as to calculate ascaling potential of the water in the recirculation loop RS in responseto a function of the chemical and/or physical property of the waterand/or the scale inhibitor concentration in the recirculation loop RS.

The scaling potential of the water may be expressed as the LangelierScaling Index, and the scaling potential of the water may be correctedfor the scale inhibitor concentration in the water in the waste wateroutlet 16 and/or in the recirculation loop RS.

The controller CN may be connected to the addition device AD2 so as toadjust the scale inhibitor dosing rate in the water entry point inresponse to the calculated scaling potential in the water in the wastewater outlet 16 and/or in the recirculation loop RS by logic circuit LC.For example if the calculated scaling potential by logic circuit LC ishigher than a threshold value the addition device AD2 may increase thedosing rate of the scale inhibitor SI.

The controller CN may be connected to the flow adjuster FA so as toadjust the water velocity in the flow through capacitor FTC in responseto the calculated scaling potential by logic circuit LC. For example ifthe calculated scaling potential by logic circuit LC is higher than athreshold value the flow adjuster FA may increase the waste water flow16 to reduce the scaling potential.

The controller CN may be connected to a power converter PC which isoperably connected to the first electrodes 13 via the first connector 17and the current collectors 14 a and with the second electrodes 15 viacurrent collectors 14 b and second connector 19. The controller CN maycontrol the power converter PC to apply less or more power to the FTC inresponse to the calculated scaling potential by logic circuit LC. Forexample if the calculated scaling potential within the FTC by logiccircuit LC is higher than a threshold value the power converter PC mayreduce the FTC power to reduce the amount of ions taken up by the flowthrough capacitor and therefore reduce the scaling potential within theFTC.

Once the electrodes of the flow through capacitor become saturated withions the capacitor may be regenerated by going in the regeneration modeby reducing the applied voltage or even reversing the polarity of theelectrodes or by shunting the electrical circuit. The energy that isreleased during the regeneration mode can be recovered and returned tothe power entry point PS. This may help to reduce the overall energyconsumption of the ion removal apparatus. During regeneration the ionsreleased from the electrodes will be release in the water in the flowthrough capacitor and flushed away to the waste water output 16 by thevalve 12. An advantage of the use of the evaporative recirculationcooling water system according to an embodiment of the invention is thatless water is needed via the make-up water system because theconcentration of dissolved species in the water of the recirculationloop may be lower with the flow through capacitor.

In the evaporative recirculation cooling water system, one or morecertain chemicals may be added in order to avoid or minimize commonproblems such as corrosion (rust), deposit formation (in the -warm- heatexchanger and cooling tower packings), and slime formation (due toexcessive microbial growth). These one or more chemicals are calledcorrosion inhibitors, scale inhibitors and microbiocides respectively.By using the flow through capacitor less water will be used from themake-up water system and flushed to the waste water output 16 so thatless chemicals may need to be added.

Corrosion inhibitors are substances which, when added in small amountsto a corrosive environment such as recirculating cooling water, reducethe rate of corrosion of the metal piping and one or more heatexchangers present in the cooling system. Corrosion inhibitors may beclassified as anodic, cathodic, or both, depending on which portion ofthe electrochemical corrosion cell they disrupt. Combining cathodic withanodic corrosion inhibitors, provides a synergy in corrosion inhibition.

Corrosion inhibitors that may be used in the evaporative recirculationcooling water system include phosphate (orthophosphate, polyphosphate orcombinations thereof), nitrite, zinc, lignosulphonate, molybdate,triazole (mercaptotriazole, benzotriazole, tollyltriazole), phosphonate(such as aminomethylenephosphonate, hydroxyethylenediphosphonate,phosphonobutane tricarboxylic acid, phosphonosuccinic acid), tannin,silicate (ionic silica and/or colloidal or polymerized silica) and/orsarcosinate.

Microbiocides are substances which, when added in small amounts torecirculating cooling water, may reduce the rate of microbial growth inthe cooling system, and avoid formation of biofouling (which causes asecondary problem such as microbially induced corrosion (MIC) and whichnegatively affects heat exchange efficiency both in cooling towers andheat exchangers). Microbiocides may be classified either as oxidizing oras non-oxidizing biocides. Typically, small amounts of more expensivenon-oxidizing biocides may be combined with larger amounts of lessexpensive oxidizing biocides. G proteins microbiocides inhibitmicroorganisms in a variety of ways. Some of these mechanisms are:altering permeability of the cell wall and/or cell membrane therebyinterfering with vital processes of the microbe, destroying ordenaturating essential proteins such as proteins involved in energyproduction of microbes, inhibition of enzyme-substrate reactions,oxidation of protein groups, etc.

Biocides that may be used in the evaporative recirculation cooling watersystem include microbiocides such as: isothiazolin, bronopol,glutaraldehyde, diethyl-m-toluamide, hydrogen peroxide, chlorinedioxide, bromochlorodimethylhydantoin, bromide activated by bleach(either sodium bromide or ammonium bromide), quaternary ammonium salts,THPS (tetrakis(hydroxymethyl)phosphonium sulfate), sodium hypochlorite,peracetic acid, DBNPA (dibromonitrilopropionamide).

Scale inhibitors are chemical compounds which, when added in smallamounts to flow through capacitors and/or evaporative recirculationcooling water systems, reduce the scaling potential of the water. Someof the mechanisms of scale inhibition are: chelation, where solublesalts are formed from cations and scale inhibitors; dispersion, whereincreased anionic charge repels crystals, and thus preventscrystallization; crystal modification, where there is buildup ofirregular shaped, less adherent crystals; and threshold inhibition,where active crystal growth sites are blocked, preventing furthergrowth.

Scale inhibitors that may be used in the evaporative cooling watersystem should not pass through the charge barrier in the flow throughcapacitor. Since the same feed stream is used for the purificationprocess as well as for the waste process, the concentration of scaleinhibitor in the purified water outlet 10 and in the waste water outlet16 is substantially equal to the concentration of scale inhibitor in thefeed stream in water inlet 7. The dosed scale inhibitor may containweakly dissociated groups, and/or have a molecular weight between 200and 20,000, between 200 and 10,000 or between 200 and 2,000.

The scale inhibitors that may be used in the evaporative cooling watersystem include scale inhibitors that are weakly dissociated and/or havea high molecular weight. The scale inhibitors may be2-Phosphonobutane-1,2,4-tricarboxylic acid (PBTC) commercially availableas Bayhibit® AM from Lanxess AG, Germany or a polymaleic acidcommercially available as Belclene® 200 from BioLab Water Additives,United Kingdom.

There are a range of scale inhibitors that may be used for thisapplication, such as: (poly)aspartic acid; acetate; NTA; TDA;(poly)carboxylic acid; STP; citrate; polycarboxylate; polyacrylate mixedwith phosphonic acid (1-hydrorxyethlyidine) bis (HEPD) & proponoic acid(GE GenGuard™); other phosphonic acid derivatives (GE Hypersperse™);carbonate; dipicolinic acid; alkyl- and alkenyl succinate; othersuccinates; THS; TDS; BHMDS; CMOS; ODS; IDS; HIDS; EDTA in combinationwith acrylic polymer and/or other organic salt (Ashlands Advantage®Plus, Amersperse™ and Ameroyal™ lines); tetrasodium(1-hydroxyethylidene)bisphosphonate, 2-phosphono-1,2,4butanetricarboxylic acid, disodium phosphate and amino-tris-methylenephosphonic acid (GE ScaleTrol™); alkaline compound with amine-likefunctionality (Nalco's PermaTreat®); mix of sodium nitrate and sodiummolybdate (Nalco 2833); and/or modified polyacrylic acid (BASF Sokalan®CP).

If the concentration of hardness ions in the water in the recirculationloop increases because of evaporation then the water may be drained viaa blow down port BO. The sensor SN may together with the logic circuitLC be used to determine the scaling potential in the water of therecirculation loop and via controller CN the valve 21 to control thedraining of the water may be opened if the scaling potential in thewater is too high. The controller CN may control the flow adjuster FA torefresh the water in the recirculation loop with water with a lowconcentration of hardness ions because the majority of the hardness ionsis removed by the FTC.

Example 1

A scale inhibitor e.g. 2-Phosphonobutane-1,2,4-tricarboxylic acid (PBTC,Bayhibit® AM) was continuously dosed into a feedstream, to achieve a 5ppm concentration of active product in the feed stream of an evaporativerecirculation cooling water system similar to FIG. 1. This feed streamwas deionized by a charge barrier flow through capacitor where thecharge barriers were ion exchange membrane materials (Fumasep FKS andFumasep FAS, from Fumatech). The flow through capacitor was set toremove 75% of the ions in the feed stream. The concentration factor ofthe flow through capacitor was set to 4.4, meaning that theconcentration of salts in the waste stream was set to 4.4 times higherthan the concentration of salts in the feed stream. The purified streamwas directed into a recirculation loop, containing a space to cool thewater in the recirculation loop by evaporation. The concentration factorin this recirculation loop was set to 5, meaning that the concentrationof dissolved solids in the recirculation loop is 5 times higher than theconcentration of dissolved solids in the purified stream coming from theflow through capacitor. The concentration of hardness and alkalinity inthe feed stream and in the purified stream coming from the flow throughcapacitor was determined with titration, the concentration of Bayhibit®AM in the feed stream and in the purified stream coming from the flowthrough capacitor was determined with chromatographic detection oforthophosphate after hydrolysis. The scale inhibitor is substantiallynot removed from the water in the feed stream.

FIG. 2 shows the concentration in mg/liter in the waste stream WS and inthe purified stream PS as measured during a testing period (t) of ascale inhibitor B, e.g., 2-Phosphonobutane-1,2,4-tricarboxylic acid(PBTC, Bayhibit® AM) continuously dosed. It shows the measuredconcentration of Bayhibit® AM for the waste stream WS as well as thepurified stream PS. The figure shows that the concentration Bayhibit® AMis substantially equal in the waste stream WS as in the purified streamPS. The scale inhibitor B is substantially not removed from the water inthe feed stream leading to substantially equal concentrations in thewaste stream WS as in the purified stream PS.

TABLE 1 Chemical composition of the waste water and purified waterstream as measured by sensors SN1 and SN2 in FIG. 1 Alkalinity HardnessConductivity Temperature Bayhibit ® AM Sensor (ppm CaCO3) (ppm CaCO3) pH(uS/cm) (deg. C.) (ppm) Waste water 2136 907 8.27 2300 25 5.3 Purifiedwater 74.5 29.89 7.625 130.75 25 5.2

The data in Table 1 can be transformed into a scaling tendency by usingthe Langelier Scaling Index, resulting in a LSI of 2.5 for the wastewater. The logic circuit linked the LSI to the current dosing rate ofBayhibit® AM, where the concentration was adjusted accordingly byincreasing or decreasing the addition of Bayhibit® AM by addition deviceAD2.

The purified water stream was fed into the cooling tower, which at acycle of concentration of 10 resulted in a Bayhibit® AM concentration of53 ppm and a conductivity in the cooling tower of 1300 uS/cm. This ismonitored by sensor SN3, and controller CN controlled the valve 21 tocontrol the draining of the water if the scaling potential in the waterwas too high.

Example 2

In the evaporative recirculation cooling water system according toExample 1, the differential pressure over the flow through capacitor wasmeasured between the inlet and the outlet of the flow through capacitor.FIG. 3 shows the measured differential pressure normalized for the flowthrough capacitor in three periods, the first period being where a scaleinhibitor was continuously dosed into the feedstream, according toExample 1, the second period being where no scale inhibitor wascontinuously dosed into the feedstream, and the third period beingwhere, after acid cleaning of the module, the concentration factor inthe flow through capacitor was reduced to allow for no scale inhibitordosing.

As can be seen from FIG. 3, in period 1 the normalized pressure is notincreasing, indicating that no scaling occurs in the flow throughcapacitor due to the dosing of scale inhibitor, which results in lowscaling tendency in the flow through capacitor. In period 2 thenormalized pressure increases rapidly, indicating that scaling occurs inthe flow through capacitor due to the lack of scale inhibitor, resultingin a higher scaling tendency in the flow through capacitor. In period 3,after acid cleaning of the module, the normalized pressure is notsignificantly increasing, indicating that no scaling occurs in the flowthrough capacitor due to the decreased concentration factor in the flowthrough capacitor, which results in lower scaling tendency in the flowthrough capacitor.

Example 3

A scale inhibitor e.g. polymaleic acid (Belclene® 200) was continuouslydosed into a feed stream being deionized by a charge barrier flowthrough capacitor of an evaporative recirculation cooling water systemsimilar to FIG. 1. The dosing rate is 3 ppm of active product. The FTCremoved 90% of the ions in the feed stream. The concentration factor ofthe FTC was 8. The concentration factor of the cooling tower was 5. Thesensor SN3 was used to determine the calcium, alkalinity and pH of thewaste stream. Using the logic circuit, the LSI of the waste stream wasdetermined to be 3. At a LSI of 3, the concentration of Belclene® 200twas deemed insufficient to prevent scaling, therefore the controller CNincreased the dosing rate of the active product to 5 ppm.

Example 4

A proprietary scale inhibitor was continuously dosed into a feedstreambeing deionized by a charge barrier flow through capacitor in anevaporative recirculation cooling water system similar to FIG. 1. Thedosing rate was 10 ppm of active product. The FTC removed 90% of theions in the feed stream. The concentration factor of the FTC was 4. Theconcentration factor of the cooling tower was 5. The sensor SN2 was usedto determine the flow rate in the waste stream. The logic circuitpredicted the waste stream composition using the predefined ingoingwater composition, the FTC removal and the FTC concentration factor,from which it calculated the LSI to be 2. At a LSI of 2 the waste flowrate was deemed too low given the scale inhibitor dosing rate, thereforethe controller CN decreased the flow rate of the waste stream to achievea concentration factor in the FTC of 6.

The descriptions above are intended to be illustrative, not limiting.Thus, it will be apparent to one skilled in the art that modificationsmay be made to the invention as described without departing from thescope of the claims set out below.

1. An evaporative recirculation cooling water system comprising: arecirculation loop to recirculate water through the system; aconstruction with a space to cool the water in the recirculation loop byevaporation; a water entry point to allow water into the recirculationloop; a charge barrier flow through capacitor constructed and arrangedto remove ions from the water between the water entry point and therecirculation loop; and a scale inhibitor dosing system downstream ofthe water entry point and upstream of the charge barrier flow throughcapacitor to dose a scale inhibitor into the water flow from the waterentry point to the charge barrier flow through capacitor.
 2. The systemaccording to claim 1, wherein the charge barrier flow through capacitorcomprises a charge barrier constructed to substantially allow notransport of weakly dissociated molecules and/or charged molecules witha molecular weight greater than
 200. 3. The system according to claim 1,wherein the scale inhibitor dosing system is constructed to dose a scaleinhibitor comprising weakly dissociated groups.
 4. The system accordingto claim 1, wherein the scale inhibitor dosing system is constructed todose a scale inhibitor having a molecular weight between 200 and 20,000.5. The system according to claim 1, wherein the scale inhibitor dosingsystem is constructed to dose a charged scale inhibitor.
 6. The systemaccording to claim 1, further comprising a sensor to measure a chemicaland/or physical property of the water in a waste water output and/or apurified water output and/or the recirculation loop.
 7. The systemaccording to claim 1, further comprising a controller configured tocontrol charging and/or discharging of a first and second electrode ofthe charge barrier flow through capacitor; and control a regulator todirect water to a purified water output during charging of the chargebarrier flow through capacitor and to a waste water output duringdischarging of the charge barrier flow through capacitor, wherein thecontroller is configured to control a flow adjuster so as to adjust thewater velocity in the charge barrier flow through capacitor in responseto a function of a chemical and/or physical property of the water in thewaste water output and/or the purified water output as measured with asensor.
 8. The system according to claim 1, further comprising a logiccircuit configured to calculate a scaling potential of waste water inresponse to a function of a chemical and/or physical property of thewater in a waste water output as measured with a sensor, as well as thewater velocity in the charge barrier flow through capacitor.
 9. Thesystem according to claim 8, comprising a controller configured tocontrol dosing of the scale inhibitor based on the scaling potential ofthe waste water as determined by the logic circuit.
 10. The systemaccording to claim 1, wherein the scale inhibitor dosing system isconstructed to continuously dose a scale inhibitor.
 11. A method ofoperating an evaporative recirculation cooling water system, the methodcomprising: recirculating water through a recirculation loop of theevaporative recirculation cooling water system; cooling the water byevaporation; adding water from a water entry point to the recirculationloop; removing ions from the water from the water entry point with acharge barrier flow through capacitor; and dosing a scale inhibitor intothe water flow from the water entry point to the charge barrier flowthrough capacitor.
 12. The method according to claim 11, wherein thecharge barrier flow through capacitor comprises a charge barriersubstantially not allowing transport of weakly dissociated moleculesand/or charged molecules with a molecular weight greater than
 200. 13.The system according to claim 11, wherein the dosing comprises dosing ascale inhibitor comprising weakly dissociated molecules.
 14. The methodaccording to claim 11, wherein the dosing comprises dosing a scaleinhibitor having a molecular weight between 200 and 20,000.
 15. Themethod according to claim 11, wherein the dosing comprises dosing acharged scale inhibitor.
 16. The method according to claim 11,comprising continuously dosing a scale inhibitor into the water flow.17. A method of operating a water deionizing system, the methodcomprising: dosing an amount of scale inhibitor into water upstream of acharge barrier flow through capacitor; and removing ions from the waterwith the dosed amount of scale inhibitor by allowing the water to flowthrough the charge barrier flow through capacitor while charging thecharge barrier flow through capacitor and directing the water from thecharge barrier flow through capacitor to an outlet after the hardnessions have been removed.
 18. The method according to claim 17, whereinthe rate of addition of the scale inhibitor is dependent on a scalingpotential of a charge barrier flow through capacitor waste water. 19.The method according to claim 17, wherein the rate of addition of thescale inhibitor is dependent on a scale inhibitor concentration in acharge barrier flow through capacitor waste water.
 20. The methodaccording to claim 17, wherein the scale inhibitor concentration isbetween 0.5 and 20 ppm.
 21. The method according to claim 17, whereinthe dosed scale inhibitor comprise a charged scale inhibitor.
 22. Themethod according to claim 17, wherein the dosed scale inhibitorcomprises weakly dissociated groups, and/or has a molecular weightbetween 200 and 20,000.
 23. The method according to claim 17, whereinthe scaling potential expressed as LSI is between 1.5 and
 4. 24. Themethod according to claim 17, wherein the charge barrier flow throughcapacitor is provided between a water entry point and a recirculationloop and the hardness ions are removed from the water of the entry pointbefore the water is provided to the recirculation loop, while leavingthe scale inhibitor in the water.
 25. The method according to claim 17,further comprising measuring with a sensor a chemical and/or physicalproperty of the water.
 26. The method according to claim 25, furthercomprising: controlling charging and/or discharging of a first andsecond electrode of the charge barrier flow through capacitor with acontroller; and controlling a regulator to direct water to a purifiedwater output during charging of the charge barrier flow throughcapacitor and to a waste water output during discharging of the chargebarrier flow through capacitor with the controller, wherein thecontroller controls a flow adjuster so as to adjust the water velocityin the charge barrier flow through capacitor in response to a functionof the chemical and/or physical property of the water in the waste wateroutput and/or the purified water output as measured with the sensor. 27.The method according to claim 17, further comprising calculating ascaling potential of the waste water in response to a function of achemical and/or physical property of the water in the waste water outputas measured with a sensor, as well as the water velocity in the chargebarrier flow through capacitor
 28. The method according to claim 27,further comprising controlling the dosing of the scale inhibitor basedon the calculated scaling potential.